A degenerative lesion of the auditory system of mongolian gerbil (Meriones unguiculatus) was reported by K.Morest et al., 1986. The lesion was evaculation confined to the cochlear nucleus (CN) and increased with age. This study was performed to explore an effect of age-related lesion in gerbil's CN on the auditory function. 30 gerbils from 21 days to 2 years and 3 months old were used. They have had no ear infection. The auditory function was electrophysiologically evaluated by recording of cochlear microphonics (CM) and auditory brain stem response (ABR). Then CN and cochlea were microscopically observed. Correlation of the occurrence of lesion was examined with change of CM and ABr.Evaculation in gerbil's CN began to appear at around 7 weeks of age and the lesion increased in number and size with age. Number of vacuoles in average was less than 5 for 7-week-old gerbils and more than 15 for over 4-month-old gerbils. Mean size of each vacuole was smaller than 50 mum^2 for the former ge
… Morerbils and became larger than 150 mum^2 for the latter. Unlikely with the age-related changes in the cochlear nucleus, no vacuole was seen in cochlea. CM thresholds of gerbils at the frequency range of 1 k - 8kHz increased with aging. The CM thresholds of 4-month-old gerbil were 20-30 dB lower than those of the over 2-year-old gerbils. Similarly with the change of CM thresholds, ABR thresholds increased 15-20 dB with their age. Latencies of ABR waves became elongated along with the increased thresholds. Inter-wave latencies between I and V were also more prolonged in over 2-year-old gerbils than in the younger gerbils. However this delay was almost same with the prolongation of latencies which was caused by the increased thresholds of ABR.The results of CM and ABR in this study showed that auditory function in the cochlea and brain stem pathway of gerbils reached adult levels at about 4 months of age and gradually decreased with age. So far we have not found the direct effect of lesions in the CN on the age-related auditory function of gerbils.3.種特異性の検討:スナネズミの蝸牛神経核での変性が種特異的なものかの確認として、Wistar系ラットとSHR-SP(脳卒中易発作性高血圧ラット)を用いて検討した。2年以上の高齢例でも、200mmHgの高血圧例でも変性は見られず、スナネズミに固有の変性と考えられた。4.中枢神経系の変性のモデルとしてのスナネズミ:アルツハイマー病などヒトの中枢神経系の変性疾患の病因は現在不明であるが、スナネズミの蝸牛神経核での経時的な変性を一つの動物モデルとしてその形態と機能の変化を研究することにより、生理的な老化による障害と病的な変性の差異を調べる可能性が明らかになった。 Less